Methods and apparatus for completing production wells

ABSTRACT

This application discloses new and improved methods and apparatus for completing production wells having perforations which either are to be cleaned or penetrate earth formations which are to be fractured, acidized, or treated such as, for example, to inhibit the subsequent production of unconsolidated formation materials. To practice the present invention, a new and improved production tool is arranged for coupling into a string of production tubing and includes a typical well packer coupled to an elongated tubular member defining an enclosed chamber of a substantial volume and which is initially maintained at a reduced pressure by a selectively-releasable tubing plug and a new and improved normally-closed valve respectively arranged at the upper and lower ends of the tubular member. The production string and the tool are installed in a cased well bore with the packer being set above a previously-perforated interval traversing an earth formation which is to be subsequently produced. Once the customary wellhead equipment is installed, the normally-closed valve is selectively opened by rotating the production string from the surface. Upon opening of this valve, formation fluids will be suddenly exhausted into the reduced-pressure chamber for removing contaminants that may have previously entered the formation following the perforation of the casing so as to leave only uncontaminated formation materials immediately surrounding the perforations. Thereafter, the tubing plug is removed to permit selected fluids to be pumped by way of the production string through the perforations and into the adjacent earth formations.

United States Patent Kisling, III

[151 3,662,833 [4 1 May 16, 1972 [54] METHODS AND APPARATUS FOR COMPLETING PRODUCTION WELLS [72] inventor:

[73] Assignee:

James W. Kisling, HI, Houston, Tex.

Schlumberger Technology Corporation, New York, NY.

[22] Filed: June3,1970

[21] Appl.No.: 43,066

Primary Examiner-Joseph H. McGlynn Atrorney-Ernest R. Archambeau, Jr., David L. Moseley, Edward M. Roney and William R. Sherman [5 7] ABSTRACT This application discloses new and improved methods and apparatus for completing production wells having perforations which either are to be cleaned or penetrate earth formations which are to be fractured, acidized, or treated such as, for example, to inhibit the subsequent production of unconsolidated formation materials. To practice the present invention, a new and improved production tool is arranged for coupling into a string of production tubing and includes a typical well packer coupled to an elongated tubular member defining an enclosed chamber of a substantial volume and which is initially maintained at a reduced pressure by a selectively-releasable tubing plug and a new and improved normally-closed valve respectively arranged at the upper and lower ends of the tubular member. The production string and the tool are installed in a cased well bore with the packer being set above a previouslyperforated interval traversing an earth formation which is to be subsequently produced. Once the customary wellhead equipment is installed, the normally-closed valve is selectively opened by rotating the production string from the surface. Upon opening of this valve, formation fluids will be suddenly exhausted into the reduced-pressure chamber for removing contaminants that may have previously entered the formation following the perforation of the casing so as to leave only uncontaminated formation materials immediately surrounding the perforations. Thereafter, the tubing plug is removed to permit selected fluids to be pumped by way of the production string through the perforations and into the adjacent earth formations.

20 Claims, 6 Drawing Figures PKTENTEDMAY 16 I972 SHEU 1 OF 3 James W Kisling, E

IN VENTOR ATTORNEY w om v PATENTEDMAY 16 m2 SHEET 2 [IF 3 Jbms W. K/sl/ng, HI

/ N VE N TOR ATTORNEY fracturing, or sand-consolidating operations METHODS AND APPARATUS FOR COMPLETING PRODUCTION WELLS It is, of course, customary for a cased well bore to be perforated at one or more points to provide fluid communication with selected earth formations therearound. Once the well is perforated, various treating operations such as acidizing, are typically conducted to prepare the well for efficient production. Those skilled in the art will appreciate, however, that it is not at all uncommon for one or more of the perforations along a given perforated interval to be at least partially blocked by loose formation materials, debris, or foreign matter which is usually deposited in a perforation by typical shaped charges. A partial or total blockage of one or more of the perforationswill, of course, impede or prohibit the introduction of treating fluids into those perforations and result in the inadequate treatment of at least those portions of the earth formation immediately adjacent thereto. As a result, further and otherwise needless treating operations will ultimately be required. Accordingly, unless all of the perforations along a perforated interval are capable of readily conducting fluids, subsequent treating operations as well as the production rate of the well will be significantly impaired.

Heretofore, such treating operations have had to be conducted before the drilling rig is removed from the well site so that its associated equipment and drill string could be employed. This, of course, results in needless expenses as well as additional delays before the production string and the related surface equipment can be installed to prepare the well for production.

Accordingly, it is an object of the present invention to provide new andimproved methods and apparatus for completing wells to obtain improved fluid communication between the well bore and selected earth formations traversed thereby without delaying the installation of the production string and the associated wellhead and surface equipment once the drilling operation is concluded.

This and other objects of the present invention are attained by arranging manuallyvactuated valve means in a production string and above a production packer included therewith. By initially closing the valve means and arranging barrier means in the string thereabove, an enclosed chamber of selected volume is defined in the interconnecting tubing therebetween which is maintained at a reduced pressure until after the packer is set and the production string is installed and connected to the usual wellhead. To prepare the well for production, the valve means are selectively opened from the surface by rotating the wellhead and production string coupled thereto to draw formation fluids into the enclosed chamber for clearing the perforations below the production packer of debris or contaminants that would otherwise impair fluid communication between the production string and the perforated earth formations. Thereafter, the barrier means are selectively released and returned to the surface so that the production string can be used for injecting fluids from the surface into the well bore below the packer as may be necessary to prepare the well for production.

In the preferred embodiment of the apparatus of the present invention, the valve means are operatively arranged to be selectively opened in response to a predetermined number of rotations of the production string above the production packer. In this manner, communication can be selectively established between the perforated interval and the enclosed chamber below the barrier means in the production string thereabove.

The novel features of the present invention are set forth with particularity in the appended claims. The invention, together with further objects and advantages thereof, may be best understood by way of the following description of new and improved apparatus and exemplary methods employing the principles of the invention as illustrated in the accompanying drawings, in which:

FIGS. 1, 3 and 4 schematically depict the successive steps of the methods of the present invention;

diill FIG. 2 shows a typical perforation as it may appear before conducting a completion operation in accordance with the methods of the present invention; and

FIGS. 5 and 6 depict a preferred embodiment of the new and improved apparatus of the present invention.

Turning now to FIG. 1, a new and improved production tool 10 arranged in accordance with the principles of the present invention is schematically illustrated as being dependently coupled from the lower end of a string of production tubing 11 and positioned in a well bore 12 having a casing 13 secured in place by an external sheath of cement 14. To gain communication with an earth formation 15 traversed by the well bore 12, one or more perforations, as at 16, have been previously produced through the casing 13 and cement 14 in the usual manner. As is customary, the production tubing is dependently supported in the well bore 12 by a typical wellhead assembly 17 including at least a pair of valves, as at 18 and 19, for selectively controlling communication with the tubing string 11 and the casing 13.

As illustrated in FIG. 1, the tool 10 is comprised of a selectively-settable production packer 20 which is dependently coupled to the lower end of a tubular body 21 to provide an enclosed chamber 22 that is initially maintained at a low or atmospheric pressure by arranging normally-closed valve means 23 at the lower end of the body and selectively-releasable barrier means 24 at the upper end of the body. As a matter of convenience, it is, of course, preferred to employ one or more joints of conventional production tubing for the elongated body 21. The chamber 22 can, if desired, be filled with an inert gas that is at a selected pressure which is less than the anticipated formation pressure. Although other well packers may, of course, be employed, it is preferred that the packer 20 be one of the production packers shown in either US. Pat. Nos. 3,074,484 or 3,352,362.

As will be subsequently discussed, the methods of the present invention are uniquely applicable for performing acidizing and fracturing operations as well as sand-consolidation operations after the production string 11 and the wellhead 17 are in position. Accordingly, as depicted in FIG. 2, an enlarged view is shown of one of the perforations 16 as it may well appear after the adjacent formation 15 has been perforated. It will, of course, be appreciated that when a perforating tool (not shown) which typically includes one or'more shaped charges is positioned in the well bore 12 and actuated for producing the perforations 16, the perforations will initially extend into the formation 15 as generally represented in FIG. 2.

In any event, irrespective of the nature of the formation, debris (such as at 25) will be left in the formation 15 as a result of the disintegration of a typical shaped charge liner. Moreover, by observing test shots fired into laboratory targets, it is known that a typical shaped charge perforating jet will leave a somewhat-impermeable layer of debris (as indicated at 26) around the walls of the forward portion of the perforation 16. This relatively-impermeable sheath of debris will either remain substantially in the position illustrated at 26; or, if the formation (as at 15) is incompetent, this impermeable layer will most likely be collapsed inwardly as the forward portion of the perforation 16 is filled with loose formation materials. In any event, flow communication between the well bore 12 and the formation 15 will be at least retarded, if not substantially impaired, by the debris 25 and 26 deposited in the perforations 16. It is, therefore, this debris 25 and 26 which, irrespective of the competency of the formation 15, must be removed before the well bore 12 can be successfully completed and production commenced.

Accordingly, as illustrated in FIG. 3, after the packer 20 has been set for isolating the interval of the well bore 12 immediately adjacent to the perforations 16 from the remainder of the well bore thereabove and the wellhead 17 is in position, the valve 23 is opened. It will be appreciated, therefore, that upon opening of the valve 23, a sudden high-pressure differential is developed between the connate fluids in the formation 15 and the enclosed chamber 22 which, preferably, is initially at atmospheric pressure. This sudden pressure differential across the perforated well bore interval will induce a rapid, high-velocity flow of connate fluids, as at 27, from the formation through the, various perforations 16 and into the empty chamber 22. These rushing fluids will, therefore, effectively wash out the debris, as at 25 and 26 (FIG. 2), along with any loose formation materials from the perforations. As a result, once this sudden flow ceases upon the filling of the chamber 22, the formation 15 surrounding the perforations 16 will be efl'ectively cleaned leaving only clean formation particles adjacent to the perforations.

It is preferred to delay the removal of the barrier means 24 after opening of the valve means 23 so as to allow loose formation particles, debris and the like to settle into the lower portion of the enclosed chamber 22 as well as into the well bore 12 therebelow. Once this is believed to have occurred, the barrier means 24 are removed to establish fluid communication between the wellhead 17 and the formation 15.

The technique employed to remove the barrier means 24 will, of course, be dependent upon the particular apparatus employed therefor. For instance, the barrier means 24 must be a so-called tubing plug" which is releasably secured in position by a shear pin or typical latching fingers in a typical landing nipple, as at 28, and adapted to be removed by a typical wireline overshot or grapple (not shown) that is lowered through the production string 11 and coupled to an upright fishing neck as at 29. This tubing plug 24 might well be one of those shown on Page 3788 of the 1968-69 "Composite Catalog of Oil Field Equipment and Services".

Once the barrier means 24 have been removed, a fluid, such as at 30 in FIG. 4, is injected into the production string 11 through the wellhead valve 18. Where the formation 15 does not require a treating operation, the fluid 30 needs only to be a suitable fluid such as a clean saline solution. By properly selecting a saline solution of sufficient density, the resulting hydrostatic pressure of the fluid 30 will alone be effective for retaining control of the well until production is commenced.

On the other hand, where the earth formation 15 is to be consolidated by typical sand-consolidating agents, it is generally preferred that the fluid 30 be a so-called pre-flush fluid such as kerosene, diesel oil, or a clean saline solution. Once the pressured pre-flush fluid 30 is pumped into the formation 15, one or more consolidating agents (not shown) are successively pumped through the tubing string 11 and into the formation to accomplish the desired consolidation. As is typical, the consolidating fluids may then be followed by a suitable after-flush agent, such as kerosene, as well as in some instances, if production is not to be commenced immediately, temporary plugging agents such as Black Magic" an oil-base mud as supplied by Oil Base, Inc., of Houston, Texas. It will be recognized that the hydrostatic pressure and the pumping pressure of these successively-injected treating fluids will be greater than the formation pressure of the formation 15 so that the perforations 16 will remain open throughout the consolidation operation. The particular nature or type of the sand-consolidation agents employed are, of course, of no significance to the present invention and the consolidating agents may be either porous-setting or solid-setting plastics.

As previously mentioned, the methods of the present invention are also equally applicable for acidizing or hydraulic fracturing operations after the wellhead 17 and the production string 11 are in position. Accordingly, where the formation 15 is to be either acidized or fractured, the fluid 30 will, of course, be the treating fluid or fluids which are typically employed for such operations. Otherwise, the sequence of events will be substantially as depicted in FIGS. 1-4 with the possible exception that the formation 15 may be sufficiently competent that there will be little or no elution of loose formation materials as the debris 25 and 26 is cleared from the perforations 16. In either situation, however, those skilled in the art will appreciate that the new and improved methods of the present invention will be of significant benefit for economically conducting either an acidizing operation or a hydraulic fracturing operation.

Turning now to FIG. 5, a preferred embodiment is shown of the new and improved production tool 10 of the present invention. Inasmuch as the preferred tool 10 is especially adapted to utilize a commercially-available tubing plug (such as previously described) for the selectively-releasable barrier means 24 and its detailed arrangement is not within the scope of the present invention, the barrier is not depicted in FIG. 5 to facilitate the description of the production tool and the valve 23. Thus, in the preferred embodiment of the production tool 10, it is preferred that the barrier means 24 be a conventional tubing plug which is adapted to be selectively released from the landing nipple 28 at the under end of the tool and retrieved to the surface by means of a typical wireline overshot or grapple (not shown).

As illustrated, the production tool 10 includes the new and improved valve 23 and the extended tubular member 21 which is coupled above the valve and has the tubing plug 24 fluidly sealing its upper end. The valve 23 includes a tubular mandrel 31 having its lower portion telescopically arranged within the upper portion of a tubular body 32 and operatively coupled thereto, as by threads 33, for axial movement in relation to the body upon rotation of the mandrel. The upper end of the body 32 is enlarged as at 34 and extended upwardly around the mandrel 31 and a fluid seal 35 is arranged therebetween to fluidly seal the mandrel in relation to the body. Threads 36 and 37 are respectively arranged on the upper end of the mandrel 31 and the lower end of the body 32 for coupling the valve 23 between the elongated body 21 and the packer 20.

As best seen in FIG. 5, a pair of valve members 38 and 39 are cooperatively arranged within the internal bores 40 and 41 of the mandrel 31 and the body 32 for selectively blocking fluid communication therebetween until rotation of the mandrel has axially shifted it in relation to the body to a position as determined by opposed shoulders 42 and 43 on the mandrel and body respectively. In the preferred embodiment of the valve 23, the valve member 38 is a sleeve coaxially disposed in the internal bore 41 and yieldably supported within the body 32 by means such as a spring 44 disposed therein between the sleeve and an inwardly-directed stop or ring 45 that is releasably coupled to the body below the sleeve. The valve member 39 is preferably an elongated cylindrical rod having an enlarged-diameter intermediate portion 46 coaxially arranged within the sleeve 38 and an enlarged-diameter upper portion 47 extending thereabove and complementally fitted within a reduced-diameter seat 48 formed in the lower end of the mandrel 31. A sealing member 49 is cooperatively arranged for fluidly sealing the enlarged portion 47 of the valve member 39 in relation to the seat 48 so long as the inner valve member remains in the position illustrated in FIG. 5. A longitudinal passage 50 is formed in the cylindrical valve member 39 and extends between the upper end of the member and one or more lateral ports 51 arranged in the enlarged intermediate portion 46. A pair of sealing members 52 and 53 are mounted around the intermediate portion 46 above and below the ports 51 and operatively engaged or seated within the sleeve 38 for blocking fluid communication through the passage 50 so long as the valve member 39 remains in the position illustrated in FIG. 5. The valve members 38 and 39 are releasably secured to one another by means such as a shear pin 54.

It will be appreciated, therefore, that so long as the several members of the valve 23 remain in their respective positions as depicted in FIG. 5, the lower end of the enclosed chamber 22 thereabove will remain closed. As previously described, the tubing plug 24 at the upper end of the interconnecting tubular member 21 will serve to isolate the upper end of the enclosed chamber 22. This is, of course, the situation representatively depicted in FIG. 1. Accordingly, as represented in FIG. 2, when the packer 20 has been set and the wellhead 17 is in position, rotation of the production tubing 11 will be effective for rotating the mandrel 31 in relation to the body 32 which is, of course, secured against rotation by the packer 20.

As best seen in FIG. 6, rotation of the mandrel 31 will be effective for progressively shifting the mandrel axially along the threads 33 until the opposed shoulders 42 and 43 are abutted. Since the sleeve 38 is initially secured to the cylindrical body 39 by the shear pin 54, the downward movement of the mandrel 31 in relation to the body 32 will shift the valve members as a unit against the spring 44 to compress the spring toward the shoulder 45. Thus, once the spring 44 has either been fully compressed or is energized'to develop ,a sufficient upwardlyacting force on the sleeve 38 to halt its further movement, the continued downward travel of the mandrel 31 and valve member 39 will fail the shear pin 54. Once the shear pin 54 fails, the spring 44 will shift the sleeve 38 upwardly in relation to the downwardly-moving cylindrical body 39 so as to uncover the ports 51 and open fluid communication into the lower end of the enclosed chamber 22 thereabove. This is, of course, the situation schematically depicted in FIG. 3.

Those skilled in the art will, of course, recognize the ad- I vantages of having a substantially uninterrupted passage through the tubing string 11 and the production tool 10 between the wellhead 17 and .the well here 12 below the packer 20 once the tubing plug 24 is subsequently removed from the landing nipple 28. Accordingly, as a further aspect of the present invention, the new and improved valve 23 is operatively arranged so that, once the ports 51 are opened, the valve members 38 and 39 will be released from the mandrel 31 and the body 32 and allowed to fall into the well bore 12 below the packer 20.

In the preferred manner of accomplishing this, the shoulder 45 is arranged as a contractible ring which is initially expanded and confined in an inwardly-directed groove 55 formed around the wall of the internal bore 41 of the body 32. To retain the contractible ring 45 in its expanded position illustrated in FIG. 5, the lower portion 56 of the valve member 39 is extended below the portsSl and cooperatively sized to be closely fitted within the ring. A groove, as at 57, is formed around thevalve member 39 between its intermediate and lower portions 46 and 56 and properly located so as to be adjacent to the contractible ring 45 as the mandrel 31 is rotated to its final position in relation to the body 32. Thus, by cooperatively sizing the ring 45 and the grooves 55 and 57, once the valve member 39 has been moved to the position depicted in FIG. 6, the contractable ring will contract into the inner groove contractible and 'be withdrawn from the outer groove 55. It will be'appreciated, therefore, that once the ring 45 is released from the outer groove 55, the valve members 38 and 39, the ring, and the spring 44 will be free to fall through the packer 20 into the well bore 12 therebelow as representatively depicted in FIG. 4.

Referring again to FIG. 1,'it will be appreciated that when the new and improved tool 10 of the present invention is positioned in the well bore 12, the tubing plug 24 will be in its initial position and the valve 23 will be in its normally-closed position as depicted in FIG. 5. The elongated body 21 will define the enclosed chamber 22 so long as the barrier 24 and the valve 23 remain in their respective positions.

As previously described in relation to FIG 3, the valve 23 is selectively opened to induce a rapid flow of connate fluids as at 27 into the enclosed chamber 22 for flushing the debris 25 and 26 from the perforations 16. To accomplish this, the tubing string 11 is rotated as required to open the ports 51 by shifting the valve member 39 downwardly to fail the shear pin 54 and allow the spring 44 to shift the sleeve above the ports. It will be recalled, of course, that the continued rotation of the production string 11 will be effective'for releasing the valve members 38 and 39 from the valve 23.

As depicted in FIG, 4, once the tubing plug 24 is removed from the production tool 10 by typical wireline retrieval techniques, the fluid can be freely injected through the production string 1 l and the now-communicated bores 40 and 41 into the well bore 12 below the packer 20 as required for the particular completion operation. It will, of course, be appreciated that should the valve members 38 and 39 fail to fall on through the packer 20, these members will be readily displaced by applying an increased fluid pressure to the production string 11. By fabricating the valve members 38 and 39 of either a metal such as aluminum or a rigid plastic material which will ultimately be disintegrated in time by the corrosive action of the well bore fluids, the debris left in the well bore 12 will be minimized.

Once the tubing plug 24 is removed from the production string 11, a continuous and substantially-uninterrupted passage is provided through the tubing string and the production tool 10 between the wellhead 17 and the well bore 12 below the packer. Thus, any so-called through tubing" completion or treating operation that is typically conducted in a production well can be readily conducted in the well bore 12 without having to remove either the wellhead 17 or the production tool 10 and its supporting string of production tubing 11.

Accordingly, it will be appreciated that the present invention has provided new and improved methods and apparatus for completing wells to obtain improved fluid communication between the well bore and selected earth formations traversed thereby without delaying the installation of the production string and the associated wellhead and surface equipment once the drilling operation is concluded. By arranging the new and improved production tool of the present invention into an otherwise-typical production string once the formation interval below the intended position of the production packer has been perforated, the wellhead and other associated surface equipment can be installed in the usual manner without further delay and the valve of the new and improved production tool of the present invention is opened to clear the perforations of debris and the like. Then, when the well is to be prepared for production, the tubing plug in the production tool is removed to establish communication from the surface with the formations below the packer. Where the formations require acidizing, fracturing or consolidation treatments to prepare the well for production, one or more treating fluids can be readily dispatched through the now-opened production string and into the well bore below the packer.

While particular illustrations and embodiments of the present invention have been shown and described, it is apparent that changes and modifications may be made without departing from this invention in its broader aspects; and, therefore, the aim in the appended claims is to cover all such changes and modifications as fall within the true spirit and scope of this invention.

What is claimed is:

1. A method for preparing a well for production of connate fluids from a well bore having a perforated interval with one or more perforation traversing earth formations and comprising the steps of: coupling a rotatably-actuated normally-closed valve between a packer and a string of production piping for selectively controlling fluid communication between said production piping and said packer; releasably positioning a fluid barrier in said production piping for defining an enclosed chamber therein above said valve which is initially at a pressure less than the expected pressure of said connate fluids so long as said valve remains closed and said fluid barrier is in position; lowering said production string into said well bore and setting said packer therein above said perforated interval for isolating said perforated interval from the remainder of said well bore thereabove; rotating said production string to open said valve for drawing said connate fluids into said chamber for expurgating said perforations; coupling the upper end of said production string to a wellhead for securing said production string in said well bore; and, thereafter, removing said fluid barrier from said production string for establishing communication therethrough between said wellhead and said perforated interval.

2. The method of claim 1 wherein at least the last of the latter two steps is not performed until shortly before production is to be commenced from the well.

3. The method of claim 1 wherein said valve is opened by increasing the pressure in said production string above said fluid barrier.

4. The method of claim 1 wherein said production string is rotated before said upper end thereof is coupled to said wellhead.

5. The method of claim 4 wherein said valve is opened by increasing the pressure in said production string above said fluid barrier.

6. The method of claim 5 wherein said upper pressure-actuated valve is not opened until production is about to be commenced from the well.

7. Apparatus adapted for producing connate fluids from earth formations traversed by a well bore and comprising: a production string positioned in said well bore between the surface and a perforated interval of said well bore having one or more perforations directed into earth formations adjacent thereto; means adapted for supporting said production string in said well bore and including a wellhead coupled to the upper end of said production string and operatively arranged for selectively controlling communication therewith; a well packer coupled in said production string and operatively arranged for packing-off said well bore above said perforated interval to provide an isolated fluid passage thereto; a fluid barrier releasably secured in said production string above said fluid passage and operatively arranged for selective retrieval to the surface by way of said production string and said wellhead; means adapted for defining an enclosed chamber in said production string between said fluid barrier and said fluid passage and including normally-closed valve means blocking communication between said fluid passage and said enclosed chamber and adapted, upon actuation, for selectively establishing fluid communication between said perforated interval and said enclosed chamber; and rotationally operable valve-actuating means arranged between said production string and said well packer and adapted for opening said valve means in response to rotation of said production string in relation to said well packer.

8. The apparatus of claim 7 wherein said valve-actuating means include upper and lower tubular bodies respectively coupled to said production string and to said well packer, means threadingly interconnecting said tubular bodies to one another and adapted for producing relative longitudinal movement therebetween upon rotation of said upper body in relation to said lower body, and means on said tubular bodies operatively associated with said valve means and adapted for opening said valve means in response to said relative longitudinal movement of said tubular bodies.

9. The apparatus of claim 7 wherein said valve-actuating means include upper and lower tubular bodies respectively coupled to said production string and to said well packer, means threadingly interconnecting said tubular bodies to one another and adapted, upon rotation of said upper body relative to said lower body, for moving said upper body between first and second longitudinally-spaced positions along said lower body, and first and second means on said upper and lower bodies respectively engaged with said valve means and operatively arranged for opening said valve means upon movement of said upper body toward its said second position.

10. The apparatus of claim 9 wherein said second means include means releasably coupling said valve-actuating means to said valve means and operatively arranged for releasing said valve means from said valve-actuating means after opening of said valve means to drop said valve means through said fluid passage into said perforated interval.

11. The apparatus of claim 9 wherein said valve means include inner and outer valve members cooperatively arranged with one another and between said first and second means for relative movement thereby from a closed position to an open position upon movement of said upper body toward its said second position, passage means in said inner valve member, and means on said outer valve member selectively cooperable with said inner valve member for blocking said passage means so long as said upper body is in its said first position and for opening said passage means upon movement of said upper body toward its said second position to establish fluid communication between said perforated interval and said enclosed chamber.

12. The apparatus of claim 11 wherein said first means include a first stop on said upper body and engaged with one of said valve members; and said second means include a second stop on said lower body, and biasing means between said second stop and the other of said valve members and adapted for shifting said valve members to their said open position upon movement of said upper body toward its said second position.

13. The apparatus of claim 12 further including means releasably retaining said valve members in their said closed position and adapted for freeing said valve members for movement to their said open position by said biasing means upon movement of said upper body toward its said second position.

14. The apparatus of claim 12 further including means releasably retaining said second stop on said lower body, and means responsive only to movement of said upper body to its said second position for releasing said second stop from said lower body to allow said valve members to fall throughsaid fluid passage into said perforated interval.

15. Apparatus adapted to be used in a well bore having at least one perforated interval traversing earth formations from which connate fluids are to be produced and transported to the surface through a string of production piping supported in the well bore by a wellhead operatively arranged at the surface for selectively controlling communication with the production piping, said apparatus comprising: an elongated body adapted for dependent coupling to a string of production piping and having a longitudinal bore therein adapted to be in communication with such a piping string; means adapted for isolating at least a portion of said longitudinal bore from such a piping string and including a seat operatively arranged around said longitudinal bore for releasably receiving a fluid barrier adapted for selective retrieval to the surface by way of such a piping string and wellhead; and valve means adapted for selectively controlling fluid communication between a perforated interval isolated by a production packer coupled below said valve means and said isolated portion of said longitudinal bore when a fluid barrier is positioned in said seat, said valve means including a tubular body adapted for tandem connection to such a production packer and telescopically arranged on the lower end of said elongated body, means threadingly coupling said bodies to one another for relative longitudinal movement upon rotation of said elongated body in relation to said tubular body, first and second means on said bodies and adapted for movement relative to one another upon relative rotation of said bodies, and inner and outer valve members arranged in said longitudinal bore between said first and second means and adapted for movement thereby between a closed position and an open position in response to said relative movement of said first and second means.

16. The apparatus of claim 15 wherein said bodies are movable longitudinally in relation to one another from a first spaced position to a second closer position upon relative rotation of said bodies; and said first and second means include first and second abutments respectively arranged on said elongated body and on said tubular body and adapted for engagement with said valve members to telescope said inner valve member into said outer valve member as said bodies are moved toward their said second position.

17. The apparatus of claim 16 further including means releasably retaining said second abutment on said tubular body, and means responsive only to movement of said bodies to their said second position for releasing said second abutment from said tubular body to allow said valve members to fall through said tubular body.

18. Valve apparatus adapted for coupling in a string of well piping and including: upper and lower tubular bodies respectively defining longitudinal passages therethrough; means threadingly coupling said bodies in tandem to one another and adapted for axially moving said bodies relative to one another between a first position and a second position upon rotation of one of said bodies in relation to the other of said bodies; valve means operatively arranged in said bodies and adapted for blocking fluid communication between said longitudinal passages so long as said bodies are in said first position and for selectively establishing fluid communication between said longitudinal passages upon axial movement of said bodies toward said second position; and means releasably securing said valve means to said lower body and adapted for releasing said valve means from said lower body in response to axial movement of said bodies to said second position to remove said valve means from said longitudinal passages.

19. Valve apparatus adapted for coupling in a string of well piping and including: upper and lower tubular bodies respectively adapted for connection in a string of well piping and defining an axial flow passage; means threadingly coupling the adjacent end portions of said tubular bodies to one another and adapted for axially moving said tubular bodies toward one another upon relative rotation therebetween; valve means in eluding upper and lower valve members telescopically arranged with one another for relative axial movement between first and second positions and coaxially disposed in said flow passage, said upper valve member having passage means therein in communication with the upper portion of said flow passage, and means on said lower valve member blocking said passage means when said valve members are in their said first position and operatively arranged to communicate said passage means with the lower portion of said flow passage upon movement of said valve members toward their said second position; valve-actuating means including first and second means on said upper and lower tubular bodies respectively and adapted for engagement with said upper and lower valve members for axially moving said valve members from their said first position to their said second position upon relative rotation of said tubular bodies; and means cooperatively arranged between said second means and said lower valve member for selectively releasing said second means from said lower tubular body upon movement of said valve members to their said second position.

20. The valve apparatus of claim 19 wherein said second means include an abutment member between said lower tubular body and said lower valve member, and means on said lower tubular body and said lower valve member cooperatively arranged for securing said abutment to said lower tubular body so long as said valve members are not in their said second position; and said releasing means include means on said lower valve member adapted for releasing said abutment member from said lower tubular body upon movement of said valve members to their said second position. 

1. A method for preparing a well for production of connate fluids from a well bore having a perforated interval with one or more perforation traversing earth formations and comprising the steps of: coupling a rotatably-actuated normally-closed valve between a packer and a string of production piping for selectively controlling fluid communication between said production piping and said packer; releasably positioning a fluid barrier in said production piping for defining an enclosed chamber therein above said valve which is initially at a pressure less than the expected pressure of said connate fluids so long as said valve remains closed and said fluid barrier is in position; lowering said production string into said well bore and setting said packer therein above said perforated interval for isolating said perforated interval from the remainder of said well bore thereabove; rotating said production string to open said valve for drawing said connate fluids into said chamber for expurgating said perforations; coupling the upper end of said production string to a wellhead for securing said production string in said well bore; and, thereafter, removing said fluid barrier from said production string for establishing communication therethrough between said wellhead and said perforated interval.
 2. The method of claim 1 wherein at least the last of the latter two steps is not performed until shortly before production is to be commenced from the well.
 3. The method of claim 1 wherein said valve is opened by increasing the pressure in said production string above said fluid barrier.
 4. The method of claim 1 wherein said production string is rotated before said upper end thereof is coupled to said wellhead.
 5. The method of claim 4 wherein said valve is opened by increasing the pressure in said production string above said fluid barrier.
 6. The method of claim 5 wherein said upper pressure-actuated valve is not opened until production is about to be commenced from the well.
 7. Apparatus adapted for producing connate fluids from earth formations traversed by a well bore and comprising: a production string positioned in said well bore between the surface and a perforated interval of said well bore having one or more perforations directed into earth formations adjacent thereto; means adapted for supporting said production string in said well bore and including a wellhead coupled to the upper end of said production string and operatively arranged for selectively controlling communication therewith; a well packer coupled in said production string and operatively arranged for packing-off said well bore above said perforated interval to provide an isolated fluid passage thereto; a fluid barrier releasably secured in said production string above said fluid passage and operatively arranged for selective retrieval to the surface by way of said production string and said wellhead; means adapted for defining an enclosed chamber in said production string between said fluid barrier and said fluid passage and including normally-closed valve means blocking communication between said fluid passage and said enclosed chamber and adapted, upon actuation, for selectively establishing fluid communication between said perforated interval and said enclosed chamber; and rotationally operable valve-actuating means arranged between said production string and said well packer and adapted for opening said valve means in response to rotation of said production string in relation to said well packer.
 8. The apparatus of claim 7 wherein said valve-actuating means include upper and lower tubular bodies respectively coupled to said production string and to said well packer, means threadingly interconnecting said tubular bodies to one another and adapted for producing relative longitudinal movement therebetween upon rotation of said upper body in relation to said lower body, and means on said tubular bodies operatively associated with said valve means and adapted for opening said valve means in response to said relative longitudinal movement of said tubular bodies.
 9. The apparatus of claim 7 wherein said valve-actuating means include upper and lower tubular bodies respectively coupled to said production string and to said well packer, means threadingly interconnecting said tubular bodies to one another and adapted, upon rotation of said upper body relative to said lower body, for moving said upper body between first and second longitudinally-spaced positions along said lower body, and first and second means on said upper and lower bodies respectively engaged with said valve means and operatively arranged for opening said valve means upon movement of said upper body toward its said second position.
 10. The apparatus of claim 9 wherein said second means include means releasably coupling said valve-actuating means to said valve means and operatively arranged for releasing said valve means from said valve-actuating means after opening of said valve means to drop said valve means through said fluid passage into said perforated interval.
 11. The apparatus of claim 9 wherein said valve means include inner and outer valve members cooperatively arranged with one another and between said first and second means for relative movement thereby from a closed position to an open position upon movement of said upper body toward its said second position, passage means in said inner valve member, and means on said outer valve member selectively cooperable with said inner valve member for blocking said passage means so long as said upper body is in its said first position and for opening said passage mEans upon movement of said upper body toward its said second position to establish fluid communication between said perforated interval and said enclosed chamber.
 12. The apparatus of claim 11 wherein said first means include a first stop on said upper body and engaged with one of said valve members; and said second means include a second stop on said lower body, and biasing means between said second stop and the other of said valve members and adapted for shifting said valve members to their said open position upon movement of said upper body toward its said second position.
 13. The apparatus of claim 12 further including means releasably retaining said valve members in their said closed position and adapted for freeing said valve members for movement to their said open position by said biasing means upon movement of said upper body toward its said second position.
 14. The apparatus of claim 12 further including means releasably retaining said second stop on said lower body, and means responsive only to movement of said upper body to its said second position for releasing said second stop from said lower body to allow said valve members to fall through said fluid passage into said perforated interval.
 15. Apparatus adapted to be used in a well bore having at least one perforated interval traversing earth formations from which connate fluids are to be produced and transported to the surface through a string of production piping supported in the well bore by a wellhead operatively arranged at the surface for selectively controlling communication with the production piping, said apparatus comprising: an elongated body adapted for dependent coupling to a string of production piping and having a longitudinal bore therein adapted to be in communication with such a piping string; means adapted for isolating at least a portion of said longitudinal bore from such a piping string and including a seat operatively arranged around said longitudinal bore for releasably receiving a fluid barrier adapted for selective retrieval to the surface by way of such a piping string and wellhead; and valve means adapted for selectively controlling fluid communication between a perforated interval isolated by a production packer coupled below said valve means and said isolated portion of said longitudinal bore when a fluid barrier is positioned in said seat, said valve means including a tubular body adapted for tandem connection to such a production packer and telescopically arranged on the lower end of said elongated body, means threadingly coupling said bodies to one another for relative longitudinal movement upon rotation of said elongated body in relation to said tubular body, first and second means on said bodies and adapted for movement relative to one another upon relative rotation of said bodies, and inner and outer valve members arranged in said longitudinal bore between said first and second means and adapted for movement thereby between a closed position and an open position in response to said relative movement of said first and second means.
 16. The apparatus of claim 15 wherein said bodies are movable longitudinally in relation to one another from a first spaced position to a second closer position upon relative rotation of said bodies; and said first and second means include first and second abutments respectively arranged on said elongated body and on said tubular body and adapted for engagement with said valve members to telescope said inner valve member into said outer valve member as said bodies are moved toward their said second position.
 17. The apparatus of claim 16 further including means releasably retaining said second abutment on said tubular body, and means responsive only to movement of said bodies to their said second position for releasing said second abutment from said tubular body to allow said valve members to fall through said tubular body.
 18. Valve apparatus adapted for coupling in a string of well piping and including: upper and lower tUbular bodies respectively defining longitudinal passages therethrough; means threadingly coupling said bodies in tandem to one another and adapted for axially moving said bodies relative to one another between a first position and a second position upon rotation of one of said bodies in relation to the other of said bodies; valve means operatively arranged in said bodies and adapted for blocking fluid communication between said longitudinal passages so long as said bodies are in said first position and for selectively establishing fluid communication between said longitudinal passages upon axial movement of said bodies toward said second position; and means releasably securing said valve means to said lower body and adapted for releasing said valve means from said lower body in response to axial movement of said bodies to said second position to remove said valve means from said longitudinal passages.
 19. Valve apparatus adapted for coupling in a string of well piping and including: upper and lower tubular bodies respectively adapted for connection in a string of well piping and defining an axial flow passage; means threadingly coupling the adjacent end portions of said tubular bodies to one another and adapted for axially moving said tubular bodies toward one another upon relative rotation therebetween; valve means including upper and lower valve members telescopically arranged with one another for relative axial movement between first and second positions and coaxially disposed in said flow passage, said upper valve member having passage means therein in communication with the upper portion of said flow passage, and means on said lower valve member blocking said passage means when said valve members are in their said first position and operatively arranged to communicate said passage means with the lower portion of said flow passage upon movement of said valve members toward their said second position; valve-actuating means including first and second means on said upper and lower tubular bodies respectively and adapted for engagement with said upper and lower valve members for axially moving said valve members from their said first position to their said second position upon relative rotation of said tubular bodies; and means cooperatively arranged between said second means and said lower valve member for selectively releasing said second means from said lower tubular body upon movement of said valve members to their said second position.
 20. The valve apparatus of claim 19 wherein said second means include an abutment member between said lower tubular body and said lower valve member, and means on said lower tubular body and said lower valve member cooperatively arranged for securing said abutment to said lower tubular body so long as said valve members are not in their said second position; and said releasing means include means on said lower valve member adapted for releasing said abutment member from said lower tubular body upon movement of said valve members to their said second position. 